1. Field of the Invention
The present invention relates generally to measuring a tire's thickness from within the tire, including thickness of aircraft tires, commercial trucking tires, and tires used in the consumer automotive industry as well as racing. More specifically, the invention relates to an apparatus that is securable to the inside of a tire and a corresponding method for measuring tire thickness, thus allowing for the operator of a vehicle to be alerted about an eminent failure of or the need to replace a failing or failed tire.
2. Description of Related Art
A tire's tread serves to improve contact between the tire and road in wet conditions. Without the grooves of the tread, water on the road surface would be trapped under the tire and cause a loss of friction resulting in hydroplaning. This is an extremely dangerous occurrence wherein braking, cornering, or abruptedly accelerating the vehicle can result in loss of control with potentially fatal results. The tread provides a route for the water to escape from under the tire and allows the tire to more effectively grip the road.
For those applications where treaded tires are used, proper tread depth is important to safely operating the vehicle, but over time the tread wears with increased usage and the tire must eventually be replaced. Failure to timely replace a worn tire can result in a tire blowout, which at high speeds may lead to significant loss of control. Most modern road tires have built-in tread wear indicators in the form of small blocks of rubber molded into the bottoms of the grooves of the tread. When the tread has worn down to where the tops of these blocks are level with the top of the tread, the tire needs to be replaced. Alternatively, a tire tread depth gauge could be used to measure the depth of the remaining tread. Both of these methods require the operator to visually inspect the tire, which is a duty that may be neglected.
But because tire tread reduces the grip on the road by reducing the contact area between the rubber and driving surface, motor racing vehicles such as stock racing cars, open-wheeled racing cars, and dragsters frequently use treadless tires, or “slicks,” to create the greatest amount of friction between the tire and the track. This allows the driver to maintain greater control at high speeds.
For those applications that use treadless tires, such as racing, the thickness of the tire material is equally important as it is for treaded tires. If the tire abnormally wears, or wears regularly but more quickly than expected, the life of the vehicle operator as well as other participants and spectators could be placed in jeopardy due to a tire failure. Accordingly, an apparatus that can measure tire thickness in various applications would aid in preventing blowouts and other tire failures, as well as increase the efficiency and reliability of performing timely maintenance on the tires.
Numerous patents and applications have addressed devices and methods for measuring tread depth. For example, U.S. Published Application 2005/0242935 (the '935 application) presents a detection and warning system wherein a conductive element is embedded in the tire tread at a predetermined level. When the tire is worn to the predetermined level of the conductive element, the conductive element breaks, and the open circuit is detected by a logic element electrically connected to the conductive element. The driver is then alerted to the need for replacing the tire.
Similarly, U.S. Pat. No. 7,095,311 (the '311 patent) presents a coding apparatus that uses a modulated reflectance technology to measure tire tread depth. By placing a thin wire loop into the tire tread at a predetermined level, the loop will be broken when the tread is worn to that level. The broken loop changes the electromagnetic response of the loop, and appropriate circuitry detects the change in frequency response and interprets that change as a certain amount of tread wear.
U.S. Pat. No. 7,119,896 (the '896 patent) also provides a method and system for measuring wear on a tire. The '896 patent discloses a system wherein electromagnetic energy is transmitted into the tire's internal space through a transmission element disposed in the tread. The length of the transmission element changes as the tire tread wears. The amount of energy transmitted into the tire's internal space is a function of the length of the transmission element. The tire tread thickness can then be determined by analyzing the amount of energy that has propagated into the tire's internal space.
U.S. Published Application 2006/0208902 (the '902 application) presents a system wherein at least one radio frequency identification (RF ID) tag is embedded in the tread of a tire. So long as the RF ID tag remains embedded within the tread, an associated RF tag reader located within the tire's inner space detects its presence and can determine that the tread is at least not worn to the known level of the RF ID tag. As the tread wears to the level of the RF ID tag, the RF ID tag is exposed and discarded from the tire and moves outside of the range of the RF tag reader. If the RF tag reader fails to detect an RF ID tag, the system knows that the tire has worn to at least the level of the missing RF ID tag.
Among other disadvantages, each of the aforementioned systems is destroyed or otherwise modified during normal operation such that it cannot be reused. For example, the conductive element of the '935 application cannot be “unbroken”; the wire loop of the '311 patent is permanently broken and cannot be reused. Similarly, the embedded transmission element of the '896 patent cannot be lengthened and reinstalled in another tire, nor can the RF ID tag of the '902 application be recovered and reinserted into a different tire. Moreover, each of the systems disclosed by these applications and patents would have limited use in treadless applications, such as tires used in motor racing, because they are specifically contemplated for use in the tire's tread. Accordingly, a need exists for a reusable apparatus for measuring tire thickness that can be removed from a worn tire and re-installed on a new tire, regardless of whether the tire is treaded or slick.